Discovery
The windows ONVIF Device Manager tool was an excellent debugging aid along with Firefox network capture. The camera does have an HTTP web application interface but the HTTP port seems to float until you statically set it.

PTZ controls seem to be based around a variant of the IPCAM protocol (decoder_control.cgi). Attached is my Vstarcam_C24S.pm control file for installation in perl5/ZoneMinder/Control. I cloned this from the Foscam FI8918W module which has most of the same control commands and operation principles.

Zoneminder setup
Zoneminder's ONVIF discovery works nicely and sets up the device using FFmpeg source type. The camera also works fine using manually set remote source type and RTSP settings, you just have to get the authentication and port sytnax correct.

Control Type = Vstarcam_C24S
Control Device = loginuse=admin&loginpas=XXXXXX
Control Address = 192.168.XX:YY:47785 - need to discover your own port and use with the window app or the browser app to statically set the IP
Auto stop timeout = 0.10 - camera PTZ is based around start continuous movement and explicit stop. Over the internet this is too slow. The autostop give a click incremental movement.

PTZ Control Details
Name = Vstarcam_C24S
Type = Remote
Protocol = Vstarcam_C24S, i.e. the perl module file name less extension
Can Wake
Can Sleep
Can Reset

Small update: After some more extensive testing and runs during the day it would seem this camera doesn't hold a very stable RTSP server. After about a day of continuous use zoneminder ends up reporting